Sliding nozzle plate and sliding nozzle device using the same

ABSTRACT

Disclosed is a sliding nozzle plate (composite sliding nozzle plate) ( 2 ) for use in a sliding nozzle device for adjusting an outflow amount of molten metal from a molten metal vessel. The sliding nozzle plate ( 2 ) comprises a sliding nozzle plate body and a tubular member ( 3 ) formed with a flange ( 3   a ) and attached to a bore (through-hole ( 1   c ′)) of the sliding nozzle plate body, and satisfies the following conditional formulas (1) and (2): 
       φ B≦φI− 5  (1);
 
       and 
       φ B−φR≦ 4  (2),
 
     where: φB is a diameter (mm) of the bore of the sliding nozzle plate body; φI is an outer diameter (mm) of the flange of the tubular member; and φR is an outer diameter (mm) of the non-flange portion of the tubular member. The composite sliding nozzle plate is capable of preventing displacement of the tubular member and molten metal penetration into a joint between the tubular member and the sliding nozzle plate body.

TECHNICAL FIELD

The present invention relates to a sliding nozzle plate (hereinafter referred to as “SN plate”) for use in a sliding nozzle device (hereinafter referred to as “SN device”) for adjusting an outflow amount of molten metal from a molten metal vessel, particularly, a SN plate comprising: a member defining a partial region surrounding a through-hole serving as a flow passage for molten metal; and a SN plate body defining a remaining region, wherein the member is formed separately from the SN plate body, and fitted into and integrated with the SN plate body (this type of SN plate will hereinafter be referred to as “composite SN plate”), and a SN device using the SN plate.

As used in this specification, the term “composite SN plate” encompasses not only a type in which the SN plate body is a recycled SN plate obtained by recycling a used SN plate, but also a type in which the SN plate body is an unused SN plate.

BACKGROUND ART

A SN device is widely used, for example, in a ladle and a tundish, because it has an advantage of being able to accurately control an outflow amount of molten metal. The SN device includes a two-plate type and a three-plate type. For example, the two-plate type SN device is equipped with a SN plate consisting of an upper plate and a lower plate, and configured to slidingly move the lower plate in an opening or closing direction to cause respective through-holes (nozzle holes) provided in the upper and lower plates to be aligned or misaligned with each other, thereby adjusting an outflow amount of molten metal.

Such a SN plate used in the SN device is damaged due to molten metal during use. In particular, a surface of the SN plate defining the through-hole for allowing molten metal to pass therethrough will be severely damaged. Such a damaged SN plate has to be replaced with a normal one. In this case, from an economic standpoint, it is necessary to recycle the damaged or used SN plate, and some techniques for the recycling have already been proposed.

For example, the following Patent Document 1 discloses a SN plate recycling method which comprises: diametrally enlarging a through-hole of a used SN plate; and attaching a tubular member having a ring-shaped flange to the diametrally-enlarged through-hole.

FIG. 2 illustrates a SN device in which a SN plate recycled by the method disclosed in the Patent Document 1 is used in a lower plate. In FIG. 2, the reference numerals 1, 2 and 3 indicate an upper plate, a recycled lower plate, and a tubular member having a ring-shaped flange 3 a, respectively.

However, when the recycled lower plate 2 having the tubular member 3 attached thereto as illustrated in FIG. 2 was used in an actual casting operation, a problem of displacement of the tubular member 3 used for recycling, and a problem of molten metal penetration into a joint 4 between the tubular member 3 and a SN plate body (i.e., a plate body of the recycled lower plate 2), occurred.

The problems of the displacement of the tubular member 3 and the molten metal penetration into the joint 4 occur in not only the recycled lower plate 2, but also any other type of composite SN plate obtainable by attaching a tubular member to a SN plate body.

LIST OF PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP 2778869B

SUMMARY OF THE INVENTION Technical Problem

In a composite SN plate obtainable by attaching a tubular member to a SN plate body, it is an object of the present invention to prevent displacement of the tubular member, and molten metal penetration into a joint between the tubular member and the SN plate body.

Solution to the technical Problem

According to one aspect of the present invention, there is provided a SN plate for use in a sliding nozzle device for adjusting an outflow amount of molten metal from a molten metal vessel. The SN plate comprises: a tubular member having a flange and defining a partial region surrounding a through-hole serving as a flow passage for molten metal; and a SN plate body defining a remaining region, wherein the tubular member is formed separately from the SN plate body, and attached to and integrated with the SN plate body via a bonding material provided at least between an outer peripheral surface of a non-flange portion of the tubular member and a bore surface of the SN plate body, and wherein the SN plate satisfies the following conditional formulas (1) and (2):

φB≦φI−5  (1)

φB−φR≦4  (2),

where: φB is a diameter (mm) of a bore of the SN plate body; φI is an outer diameter (mm) of the flange of the tubular member; and φR is an outer diameter (mm) of the non-flange portion of the tubular member.

The present invention will be described in detail below.

Through various tests where the recycled lower plate 2 described in connection with FIG. 2 was employed as one type of composite SN plate and used in an actual casting operation, the inventors of the present invention found that a dominant factor causing displacement of the tubular member 3 used in the recycled lower plate 2 is an upward force based on a bayonet clamping force applied from a lower nozzle 5 joined to a lower portion of the tubular member 3. That is, it was found that, although the recycled lower plate 2 is also applied with a downward force based on a surface pressure loaded between the upper and lower plates, and a molten steel stream, a force to be applied to the tubular member 3 is dominated by an upward force based on a bayonet clamping force applied from the lower nozzle 5, and the problem of displacement of the tubular member 3 during use (during casting) is caused by the upward force.

Therefore, the inventors conducted various studies to prevent displacement of the tubular member 3 due to the upward force. As a result, it was found that a key point is to manage a contact width between the flange 3 a of the tubular member 3 and the plate body (SN plate body) of the recycled lower plate 2. Further, through tests repeatedly carried out under actual casting operations, the inventors have found that the displacement of the tubular member 3 can be prevented by ensuring a contact width of 2.5 mm or more. This condition is expressed as the above conditional formula (1).

In regard to the molten metal penetration into the joint, it was found that the joint 4 is inevitably exposed to molten steel stream as illustrated in FIG. 2, which accelerates corrosion, resulting in occurrence of the molten metal penetration into the joint. It was also found that a key point for preventing the molten metal penetration into the joint is to manage a thickness of the joint. As a verification result, the inventors have found that it is necessary to manage the thickness of the joint in such a manner as to become equal to or less than 2 mm. This condition is expressed as the above conditional formula (2).

As above, a composite SN plate is configured to satisfy the conditional formulas (1) and (2). This makes it possible to prevent displacement of a tubular member used therein, and molten metal penetration into a joint between the tubular member and a SN plate body.

In the sliding nozzle plate of the present invention, a recycled SN plate obtained by recycling a used SN plate may be used as the SN plate body. In this case, in order to improve a recyclability rate of used SN plates, it is preferable that the sliding nozzle plate further satisfies the following conditional formula (3): φB−φD≧30.

In the above conditional formula (3), φD is an inner diameter (mm) of the tubular member, which has a dimension equal to an inner diameter of a through-hole (nozzle hole) of the used SN plate. In an operation of recycling a used SN plate, a though-hole of the used SN plate is enlarged by boring so as to allow the tubular member to be attached thereto. The right side (φB−φD) in the conditional formula (3) is equal to two times of a boring width. More specifically, when the boring width is set to 15 mm or more, it becomes possible to reliably remove a damaged area in a through-hole (nozzle hole) defining refractory region of the used SN plate, thereby improving a recyclability rate, as described in detail later.

As mentioned above, the tubular member 3 is applied with a surface pressure loaded between the upper and lower plates and a downward force caused by a molten steel stream, as well as an upward force based on a bayonet clamping force applied from the lower nozzle 5. Then, for example, when the bayonet clamping force is lowered, a downward force can go beyond an upward force. In this situation, the tubular member 3 is likely to be displaced downwardly. In order to prevent the downward displacement of the tubular member 3, it is preferable to use, as the bonding material for forming the joint 4 between the tubular member 3 and the SN plate body, a type having excellent bonding strength, specifically, a mortar containing metal aluminum and carbon. That is, the mortar contains metal aluminum in addition to carbon, so that they react with each other by heat received during an actual casting operation to form an aluminum-carbon bond. This makes it possible to increase the bonding strength, thereby more enhancing resistance to displacement (hereinafter referred to as “displacement resistance”) of the tubular member 3.

The joint 4 made of the mortar is required to have excellent corrosion resistance because it is exposed to a molten metal outflow pathway, i.e., molten metal, as illustrated in FIG. 2. Generally, as compared to the upper plate 1 and the tubular member 3, mortar is low in strength, and low in density because it is not compressed, for example, by pressing. Therefore, as compared to the SN plate body and the tubular member 3, mortar is more likely to undergo corrosion by molten metal. Thus, the corrosion resistance of the joint 4 (mortar) is a critical required property.

In a preferred embodiment of the present invention, a carbon-containing mortar is used as the bonding material to allow the joint to have corrosion resistance. Generally, a large part of inclusions in molten metal consists of low melting point oxides. Thus, the low melting point oxides react with a refractory material, thereby accelerating degradation of a surface of a plate brick. For this reason, it is a common practice to use a carbon-containing refractory material as the plate brick and further subject the refractory material to a pitch impregnation treatment, in order to lower wettability with respect to the above oxides. The same applies to the mortar for the joint. As compared to a refractory material (carbon-containing refractory material) forming the SN plate body and the tubular member 3, a carbon-free mortar is more likely to form a layer as a product of a contact reaction with the oxides, so that corrosion in the joint is more likely to occur precedingly, thereby causing surface roughening reaching the SN plate body and the tubular member. In contrast, in the carbon-containing mortar, carbon has low wettability with respect to an oxide and functions as a barrier to suppress the formation of the layer as a product of a contact reaction with the oxides, so that it becomes possible to reduce abnormal wear (enlargement of the reaction layer), thereby solving the problem of surface roughening.

In addition to carbon, mortar suitably usable in the present invention contains metal aluminum. It is known that aluminum is capable of incorporating oxygen contained in molten metal to render it harmless, and providing enhanced corrosion resistance when it is added into a refractory material, because it has excellent deoxidation ability under refining of molten steel. Mortar for the joint can also be enhanced in corrosion resistance by adding metal aluminum thereto. In addition, the coexistence of metal aluminum and carbon allows the metal aluminum and the carbon to react with each other by heat received during an actual casting operation to form an aluminum-carbon bond, as mentioned above, thereby enhancing bonding strength.

In order to significantly exert the above advantageous effects, the mortar for use in the present invention preferably contains metal aluminum in the range of 1 to 15 mass %, and carbon in the range of 1 to 15 mass %.

Further, with a view to increasing the displacement resistance of the tubular member 3, a plurality of annular grooves 3 b may be formed in the outer peripheral surface of the non-flange portion of the tubular member 3, in a multistage manner, as illustrated in FIG. 6. This makes it possible to increase a bonding surface, thereby increasing the displacement resistance of the tubular member 3.

The SN plate (composite SN plate) of the present invention body is suitably usable as a lower plate of a SN device. That is, according to another aspect of the present invention, there is provided a SN device which comprises, as a lower plate, the sliding nozzle plate of the present invention.

Effect of the Invention

In the present invention, a composite SN plate is configured to satisfy the conditional formulas (1) and (2). This makes it possible to prevent displacement of a tubular member used therein, and molten metal penetration into a joint between the tubular member and a SN plate body.

In the present invention, a recycled SN plate obtained by recycling a used SN plate may be used as the SN plate body. In this case, the composite SN plate may be configured to further satisfy the conditional formula (3). This makes it possible to improve a recyclability rate of used SN plates.

Further, in the present invention, a mortar containing metal aluminum and carbon may be used as the bonding material provided between the tubular member and the SN plate body. This makes it possible to prevent abnormal wear of the joint, and displacement of the tubular member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) illustrates a used upper plate, and FIG. 1( b) illustrates a recycled lower plate (composite SN plate) which is a lower plate using a plate body obtained by recycling the used upper plate in FIG. 1( a).

FIG. 2 illustrates a SN device using a composite SN plate only as a lower plate.

FIG. 3 illustrates a SN device using a composite SN plate as each of a lower plate and an upper plate.

FIG. 4 illustrated a range of observation for determining the presence or absence of a crack, in evaluation of recyclability rate.

FIG. 5 illustrates a relationship between a recyclability rate and “ΦB (a diameter of a diametrally-enlarged through-hole)−φD (an inner diameter (mm) of a tubular member)” which is equal to two times of a boring width.

FIG. 6 illustrates a recycled lower plate (composite SN plate) which comprises a tubular member having a plurality of annular grooves formed in an outer peripheral surface of a non-flange portion thereof in a multistage manner.

DESCRIPTION OF EMBODIMENTS

First of all, by taking a composite SN plate using, as a SN plate body, a recycled SN plate obtained by recycling a used SN plate, as an example of a composite SN plate of the present invention, a production method for the composite SN plate will be described. FIG. 1( a) illustrates a used upper plate, and FIG. 1( b) illustrates a recycled lower plate (composite SN plate) using, as a plate body thereof, a recycled SN plate obtained by recycling the used upper plate in FIG. 1( a).

This recycled lower plate can be produced in the same manner as that described in the Patent Document 1. Firstly, a through-hole 1 b as a nozzle hole formed in a boss portion 1 a of the used upper plate 1 illustrated in FIG. 1( a) is diametrally enlarged by boring. Then, a tubular member 3 having a ring-shaped flange 3 a is attached to a diametrally-enlarged through-hole 1 b′, from the side of a surface previously used as a sliding surface 1 c, through a joint 4 (bonding material). Subsequently, the boss portion 1 a is removed by grinding, to form a new sliding surface 1 c′. In this manner, a recycled lower plate 2 is obtained.

The recycled lower plate 2 produced in the above manner is configured to satisfy the following conditional formulas (1) to (3) set forth in the appended claims:

φB≦φI−5  (1)

φB−φR≦4  (2)

φB−φD≧30  (3)

In the above formulas, φB is a diameter (mm) of the diametrally-enlarged through-hole 1 b′, and is equal to a boring diameter of the through-hole 1 b, i.e., a diameter of a bore of the SN plate body. Further, φI is an outer diameter (mm) of the flange 3 a of the tubular member 3, and is equal to a diameter of a base edge of a boss portion of an unused lower plate. That is, in the recycled lower plate 2, the flange 3 a is provided to serve as a boss portion, and adapted to be fitted with a lower nozzle 5, as illustrated in FIG. 2. φR is an outer diameter (mm) of the non-flange portion of the tubular member, and φD is an inner diameter (mm) of the tubular member.

As can be well understood by referring to FIG. 1, the conditional formula (1) expresses a condition that a contact width between the flange 3 a of the tubular member 3 and the plate body of the recycled lower plate 2 is set to 2.5 mm or more. Further, the conditional formula (2) expresses a condition that a thickness of the joint is set to 2 mm or less. The conditional formula (3) expresses a condition that a boring width is set to 15 mm or more.

Preferably, a composite SN plate of the present invention is used as a lower plate as illustrated in FIG. 2. The composite SN plate of the present invention may also be used as an upper plate. In this case, however, as illustrated in FIG. 3, a joint 4 (bonding material) of the upper plate 1 is exposed to a negative pressure region N produced by a molten steel stream, which brings concern about entry of outside air via the joint 4. Therefore, it is preferable that the composite SN plate is used as a lower plate, and an unused SN plate is used as an upper plate, as illustrated in FIG. 2.

In the composite SN plate of the present invention, an unused SN plate may also be used as the SN plate body. In this case, a SN plate with a bore having the same diameter as the diametrally-enlarged through-hole 1 b′ illustrated in FIG. 1( b) is newly prepared, and the tubular member 3 is attached to the unused SN plate.

EXAMPLES Example A

In Example A, an influence of each dimension of a composite SN plate on displacement of a tubular member used therein, and molten metal penetration into a joint between the tubular member and a SN plate body, was analyzed. A result of the analysis is illustrated in Table 1. A composite SN plate in Example A was used as a lower plate of a SN device for a ladle. The composite SN plate was made of a conventional alumina-carbon based material.

TABLE 1 Inventive Inventive Inventive Inventive Inventive Comparative Comparative sample 1 sample 2 sample 3 sample 4 sample 5 example 1 example 2 φB: Diameter (mm) of diametrally- 150 175 180 130 130 182 130 enlarged through-hole φI: Outer diameter (mm) of flangs of 185 185 185 140 140 185 140 tubular member φR: Outer diameter (mm) of non-flange 148 173 178 128 126 180 124 portion of tubular member φD: Inner diameter (mm) of tubular 90 90 90 80 80 90 80 member Satisfaction of conditional formula (1) ◯ ◯ ◯ ◯ ◯ X ◯ (φB ≦ φI − 5)*1 Satisfaction of conditional formula (2) ◯ ◯ ◯ ◯ ◯ ◯ X (φB − φR ≦ 4)*1 Observed abnormality No No No No No abnormality Displacement of Molten metal abnormality abnormality abnormality abnormality tubular member penetration into joint *1◯: The conditional formula is satisfied. X: The conditional formula is not satisfied.

In all of the inventive samples 1 to 5 illustrated in Table 1 each satisfying both the conditional formulas (1) and (2), no abnormality was observed during use. In contract, in the comparative sample 1 failing to satisfy the conditional formula (1), displacement of a tubular member occurred during use. In the comparative sample 2 failing to satisfy the conditional formula (2), molten metal penetration into a joint occurred during use.

Example B

In Example B, in a SN plate where a recycled SN plate obtained by recycling a used SN plate is used as a SN plate body, an influence of a boring width of a through-hole (nozzle hole) of the used SN plate on a recyclability rate of used SN plates was analyzed.

The recyclability rate was evaluated in the following manner. A through-hole (nozzle hole) of a used SN plate was diametrally enlarged by means of boring. In a bore surface of the diametrally-enlarged through-hole, a region in an angular range of 90 degree on a leading side of a sliding movement in an opening stroke direction (range indicated by A in FIG. 4) was observed. Then, a sample having no open crack was evaluated as “recyclable”. Specifically, a crack having a gap of 0.5 mm or more was determined to be an open crack. This is because, as long as a crack has a gap of less than about 0.5 mm, the molten metal penetration will never occur, even if molten steel contacts the crack. The above operation was performed for 100 used SN plates under the same boring conditions, and a rate of samples evaluated as “recyclable” was used as a recyclability rate.

FIG. 5 illustrates a relationship between a recyclability rate and “φB (a diameter of a diametrally-enlarged through-hole)−φD (an inner diameter (mm) of a tubular member)” which is equal to two times of a boring width. FIG. 5 shows that a high recyclability rate of about 70% or more can be obtained by satisfying the relationship: φB−φD≧30, i.e., the conditional formula (3). FIG. 5 also shows that a higher recyclability rate of about 80% or more can be obtained by satisfying the relationship: φB−φD≧40.

Example C

In Example C, a plurality of types of recycled lower plates were prepared by changing a type of mortar (bonding material) to be formed as the joint 4 between the tubular member 3 and the SN plate body in the recycled lower plate 2 illustrated in FIG. 1( b). Then, each of the plurality of types of recycled lower plates was used as a lower plate of a SN device as illustrated in FIG. 2, and compared to an unused lower plate, in terms of usable life. In all of the samples, a width of the joint was set to 2 mm.

A result of the comparison is illustrated in Table 2. In Table 2, the usable life non-attainment rate represents a rate of samples failing to attain the same usable life as that in an unused lower plate. In each of the samples, the number of tests to be assigned to the denominator was 100.

TABLE 2 Inventive sample 6 Inventive sample 7 Inventive sample 8 Inventive sample 9 Type of mortar metal Al + phenolic metal Al + phenolic metal Al + phenolic liquid glass based resin based mortar resin based mortar resin based mortar mortar Content Al2O3 90 85 80 90 (mass %) metal Al 3 5 10 0 C 3 5 5 0 Usable life 20/100 5/100 5/100 50/100 non-attainment rate

In the inventive samples 6 to 8, as a mortar containing metal aluminum and carbon, a “metal Al+phenolic resin based mortar” containing metal aluminum and phenolic resin as a carbon source, with the remainder being primarily of alumina, was used, and respective amounts (contents) of metal aluminum and carbon were changed as illustrated in Table 2.

On the other hand, in the inventive sample 9, a “liquid glass based mortar” commonly used in refractory materials was used. The liquid glass based mortar consists primarily of alumina, and contains neither metal aluminum nor carbon.

As shown in Table 2, the inventive samples 6 to 8 using the mortar containing metal aluminum and carbon had an excellent result, i.e., a low usable life non-attainment rate, as compared to the inventive sample 9 using the liquid glass based mortar. Particularly, in the inventive samples 7 and 8 where the content of metal aluminum is 5 mass % or more, the usable life non-attainment rate was significantly low, which verified the effectiveness of the mortar containing metal aluminum and carbon.

EXPLANATION OF CODES

-   1: upper plate -   1 a: boss portion -   1 b: through-hole (nozzle hole) -   1 b′: diametrally-enlarged through-hole -   1 c: sliding surface -   1 c′: new sliding surface -   2: recycled lower plate (composite SN plate) -   3: tubular member -   3 a: flange -   3 b: annular groove -   4: joint (mortar) -   5: lower nozzle -   N: negative pressure region 

1. A sliding nozzle plate usable in a sliding nozzle device for adjusting an outflow amount of molten metal from a molten metal vessel, comprising: a tubular member having a flange and defining a partial region surrounding a through-hole serving as a flow passage for molten metal; and a sliding nozzle plate body defining a remaining region, wherein the tubular member is formed separately from the sliding nozzle plate body, and attached to and integrated with the sliding nozzle plate body via a bonding material provided at least between an outer peripheral surface of a non-flange portion of the tubular member and a bore surface of the sliding nozzle plate body, and wherein the sliding nozzle plate satisfies the following conditional formulas (1) and (2): φB≦φI−5   (1) φB−φR≦4   (2), where: φB is a diameter (mm) of a bore of the sliding nozzle plate body; φI is an outer diameter (mm) of the flange of the tubular member; and φR is an outer diameter (mm) of the non-flange portion of the tubular member.
 2. The sliding nozzle plate as defined in claim 1, which further satisfies the following conditional formula (3): φB−φD≧30  (3), where φD is an inner diameter (mm) of the tubular member.
 3. The sliding nozzle plate as defined in claim 1, wherein the bonding material is a mortar containing metal aluminum and carbon, and wherein a part of the mortar is subjected to a contact with molten metal.
 4. The sliding nozzle plate as defined in claim 1, wherein the outer peripheral surface of the non-flange portion of the tubular member has a plurality of annular grooves formed in a multistage manner.
 5. The sliding nozzle plate as defined in claim 1, wherein the sliding nozzle plate body is a recycled sliding nozzle plate obtained by recycling a used sliding nozzle plate.
 6. A sliding nozzle device comprising, as a lower plate, the sliding nozzle plate as defined in claim
 1. 